At $0 subsidized you would be getting ripped off. You'd be better off buying a subsidized iPhone, selling it, then buying the G at full price (plus pocketing a bunch of $$ at the same time).
Sure, but there's so much differential that it would make sense to buy a 5S on a contract using a payday loan, put it on eBay, and then use the proceeds to pay off the expensive loan, buy the Moto G, and go buy a bunch of groceries for your family with the difference.
The Moto G would be a straight-up ripoff on a traditional contract. I expect it to be a hit in the prepaid market, however.